The problem is demonstrated in the comments of https://bugs.webkit.org/show_bug.cgi?id=66687. Due to http://trac.webkit.org/changeset/116245, bugs are getting stamped with "Re-opened since this is blocked by <bug number>" if a new bug is created and set to block it. This happens whether or not the blocked bug was already open.
Change the behavior to only do the re-open and stamp if the blocked bug was already resolved.